component

MCP23008

Public Made by Adom

by adom

Microchip 8-bit I2C I/O expander, SOIC-18W. Eight I/O with interrupt output, three address pins, 1.8-5.5 V. Datasheet-verified.

componentinterfaceio-expandergpio-expanderi2csoic-18microchip
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Datasheet

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Contents

README

markdown

MCP23008

Microchip · I2C I/O expander · SOIC-18W

Adds eight general-purpose I/O pins to a host over I2C. Each of the eight pins (GP0-GP7) is independently set as input or output, with optional pull-ups and per-pin interrupt-on-change that flags a change on the INT output, so the host is told which pin moved without polling. Three address pins (A0-A2) put up to eight devices on one bus. The 8-bit sibling of the MCP23017, at half the pins.

Pinout

Pin Name Type Function
1 SCL input I2C serial clock input. Supports Standard-mode (100 kHz), Fast-mode (400 kHz) and High-speed mode (1.7 MHz). Requires an external pull-up resistor to VDD.
2 SDA bidirectional I2C serial data (open-drain, bidirectional). Requires an external pull-up resistor to VDD.
3 A2 input Hardware address input bit 2. Sets the upper I2C slave-address bit of the MCP23008 (base address 0100 A2 A1 A0). Must be biased externally to VDD or VSS.
4 A1 input Hardware address input bit 1. Must be biased externally to VDD or VSS.
5 A0 input Hardware address input bit 0. Must be biased externally to VDD or VSS.
6 RESET input External active-low reset input. Drive low to reset the device; hold high (or tie to VDD) for normal operation.
7 NC unconnected No connect on the MCP23008 (this pin is the SPI chip-select CS on the MCP23S08 variant). Leave floating or tie to VDD/VSS.
8 INT output Interrupt output. Configurable as active-high, active-low, or open-drain via the IOCON register. Asserted on GPIO input change or mismatch vs DEFVAL.
9 VSS power_in Ground reference (0 V).
10 GP0 bidirectional General-purpose bidirectional I/O bit 0. Individually configurable as input or output; supports interrupt-on-change and an internal weak pull-up to VDD.
11 GP1 bidirectional General-purpose bidirectional I/O bit 1. Interrupt-on-change and internal weak pull-up available.
12 GP2 bidirectional General-purpose bidirectional I/O bit 2. Interrupt-on-change and internal weak pull-up available.
13 GP3 bidirectional General-purpose bidirectional I/O bit 3. Interrupt-on-change and internal weak pull-up available.
14 GP4 bidirectional General-purpose bidirectional I/O bit 4. Interrupt-on-change and internal weak pull-up available.
15 GP5 bidirectional General-purpose bidirectional I/O bit 5. Interrupt-on-change and internal weak pull-up available.
16 GP6 bidirectional General-purpose bidirectional I/O bit 6. Interrupt-on-change and internal weak pull-up available.
17 GP7 bidirectional General-purpose bidirectional I/O bit 7. Interrupt-on-change and internal weak pull-up available.
18 VDD power_in Supply voltage. Operating range 1.8 V to 5.5 V (I2C speed derated at lower voltages: 100 kHz min at 1.8 V, 400 kHz at 2.7 V, 1.7 MHz at 4.5 V). Decouple to VSS with a 0.1 µF ceramic near the pin.

Key specifications

Parameter Value
Type 8-bit I2C I/O expander
Interface I2C (up to 1.7 MHz)
I/O 8 pins (GP0-GP7), input or output
Interrupt INT output, interrupt-on-change per pin
Addresses 8 (A0-A2)
Pull-ups Software-enabled per pin (100 kΩ)
Supply 1.8-5.5 V
Package SOIC-18W (300 mil)

Ordering variants

Same part, different packaging or reel option.

  • MCP23008-E/SO (SOIC-18W)
  • MCP23008-E/P (PDIP-18)
  • MCP23008-E/SS (SSOP-20)
  • MCP23008-E/ML (QFN-20)

CAD (KiCad official)

  • Symbol: Interface_Expansion:MCP23008-xSO (KiCad official)
  • Footprint: Package_SO:SOIC-18W_7.5x11.6mm_P1.27mm
  • 3D model: SOIC-18W (KiCad packages3D, STEP)
  • 3D model files: mcp23008-etched.step / mcp23008-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); mcp23008.step / mcp23008.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Microchip datasheet (43 pp, sha256 3516fba5df6da78c, retrieved 2026-08-17, tier: manufacturer)
  • Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF